Skip to content

Organisation of the Organism

Cell Structure

Cambridge IGCSE Biology

Plant and animal cells

Struc­tureAnimalPlantFunc­tion
Nucleusyesyescontains DNA; controls the activity of the cell
Cytoplasmyesyeswhere chemical reactions take place
Cell mem­braneyesyescontrols what goes into and out of the cell
Mito­chondriayesyesaerobic respiration
Ribosomesyesyesprotein synthesis
Chloro­plastsyesphotosynthesis
Vacuolesmalllarge permanentcontains cell sap; stores water
Cell wallyesprovides support; prevents the cell bursting
  • In plant cells but not animal cells: cell wall, chloroplasts, large permanent vacuole.
  • The plant cell wall is a cellulose cell wall.
NucleusCell membraneRibosomeMitochondrionCytoplasm
An animal cell.
ChloroplastCell membraneCytoplasmNucleusCell wallVacuoleRibosomeMitochondrion
A plant cell: the structures of an animal cell, plus a cell wall, chloroplasts and a large permanent vacuole.

Bacterial cells

  • Structures: cell wall, cell membrane, cytoplasm, ribosomes, circular DNA, plasmids.
  • The DNA is free in the cytoplasm: there is no nucleus.
  • There are no mitochondria.
  • Plasmids are used in genetic modification.
  • A flagellum is used for movement.
Circular DNACell membranePlasmidCell wallCytoplasmPlasmid
A bacterial cell: circular DNA and plasmids, free in the cytoplasm, with no nucleus.

Specialised cells

CellFunction
Ciliated cell, in the trachea and bronchicilia move mucus
Root hair cellabsorption
Palisade mesophyll cellphotosynthesis
Neuroneconduction of electrical impulses
Red blood celltransports oxygen
Sperm and egg cells (gametes)reproduction

Levels of organisation

LevelMeaningExample
Cellthe smallest unit of an organismred blood cell
Tissuea group of cells with similar structures, working together to perform a shared functionintestinal epithelium
Organa structure made up of a group of tissues, working together to perform a specific functionileum, gall bladder
Organ systema group of organs working together to perform a functiongas exchange system
Organisma living thinga human

New cells are produced by division of existing cells.

These notes are part of an Excel with Osman subscription and are not available to print.

That was one page of 44

The rest of Cambridge IGCSE Biology is written the same way

The other 43 pages of Cambridge IGCSE Biology are written exactly like this one, with the mark scheme wording highlighted throughout. A year of the whole course is $6.99.

Get all 44 pages — $6.99 a yearNext free page: Magnification and Size of Specimens

Subscriptions open as soon as payment processing is approved.